ISAAC and SOFI

On this photo, two major astronomical instruments equipped with state of the art infrared array detectors are seen undergoing final integration and testing at the Assembly Laboratory at the ESO Headquarters (Garching, Germany) prior to being shipped to the ESO observatories in Chile. It was obtained a few days after a visit to this laboratory by the ESO Council at the time of its June 1997 meeting in Garching. The larger one in the foreground, ISAAC (Infrared Spectrometer And Array Camera), is destined for the VLT (Very Large Telescope) at the Paranal Observatory where it is currently used to make both infrared images and spectra at wavelengths up to 5 microns (about seven times longer than can be seen by the human eye). For maximum sensitivity the complete optical system is housed in the large vacuum vessel seen in the photo (with a diameter about 1.7-m) and cooled to a temperature of -200 o C. One of the main scientific goals of ISAAC is the detection of distant, primeval galaxies whose light has been red-shifted into the infrared region by the expansion of the Universe since the Big Bang. The smaller instrument (in the background) that is known as SOFI, is similar but is restricted to shorter infrared wavelengths and was mounted on the NTT (New Technology Telescope) at ESO's La Silla Observatory around the end of 1997. Although less sensitive, due to the smaller size (3.5-m) of the telescope, this instrument has a larger field of view which is exploited to search for distant galaxies and other objects which can then be studied in more detail with ISAAC at the VLT.